Projection systems are utilized in many aspects of modern life and provide a wide range of functionality to users. A projector may be included in a projection system to display images on a screen or other display device. A projection system may also be included in a rear-projection television or in a home theater system. Projectors utilize light sources, optical systems, and controllers to display images on a viewing surface, such as a wall or screen, for viewing by a group of people. They are especially popular among business users who give presentations. A projection system, such as a digital projector, may have illumination and imaging systems manufactured with refractive optical elements or reflective optical elements or some combination of both. These optical elements can be susceptible to degradation of performance due to contaminants such as airborne dust from the environment. Dust collecting on optical components is a major problem with optics designs such as those designs using first-surface-coated mirror optics.
Many existing projectors are intended to be used with relatively large screens. A large, permanently mounted screen is not always desirable in small areas, especially in a home environment such as a living room, because such large permanently mounted screens are often aesthetically unpleasing and obtrusive as well as difficult to hide when not in use. Most users would not choose to permanently mount a large screen in front of a window, as the screen would obscure the view through the window. There is a need for projection systems overcoming these shortcomings of the prior art.